1. Field of Invention
The invention relates to a device that develops an image electrophotographically using a developing agent.
2. Description of Related Art
In a well-known developing device, an electrostatic latent image formed on the surface of a photosensitive drum is developed by electrostatically depositing toner carried on the surface of a developing roller onto the latent image. Toner leaks in the developing device frequently cause problems. Leaking toner may contaminate the inside of an image forming apparatus and result in poor printing, or may stain an operator""s hands or clothes.
Particularly, when a non-magnetic one-component toner is used, toner is held on the surface of the developing roller mainly by intermolecular forces and may leak when the developing roller receives even a slight impact or is inclined.
To prevent such toner leaks, toner leak prevention members are provided inside the developing device. Particularly, to prevent toner leaks from both ends of the developing roller, toner leak prevention members called side seals are provided so as to make sliding contact with a circumferential surface of the developing roller at its both ends.
The side seals are formed by bonding a sliding contact member made of TEFLON(copyright) felt to a urethane spongy material. The urethane spongy material is required to be sufficiently soft and less likely to deform permanently due to compression. The sliding contact member is used to provide adequate pressing force and reduce rotation torque. However, when such side seals are used, a problem arises in that the side seals generate noise when they make sliding contact with the developing roller.
The invention intends to reliably prevent not only noise generated during sliding contact between the developing roller and the side seals but also toner leaks.
In a developing device according to the invention, a sliding contact surface of each developing agent prevention member makes sliding contact with a developing agent carrier at its either end. Accordingly, the developing agent is prevented from leaking from the sliding contact portions. In addition, as a lubricating agent is applied to the sliding contact surfaces, noise is prevented from generating when the sliding contact surfaces contact the developing roller.
The developing agent prevention members are made of a fluorine-based resin in fiber form. Accordingly, the lubricating agent efficiently enters the fibers of the developing agent prevention members and improves their noise preventing effect and developing agent leak preventing effect.
Further, when the direction of fibers on the sliding contact surfaces are previously aligned with the rotation direction of the developing agent carrier, the developing agent moving perpendicularly to the rotation direction is more reliably prevented from entering the sliding contact surfaces.
At least a fluorine-based resin such as polytetrafluoroethylene (PTFE), is preferably contained in the lubricating agent applied to the sliding contact surfaces. A fluorine oil is more preferably contained in the lubricating agent. In an embodiment of the invention, xe2x80x9cHanarl FL-Z75xe2x80x9d (80-90 wt. % hydrofluorocarbon and 10-20 wt. % polytetrafluoroethylene), made by Kanto Kasai Ltd., is used as the lubricating agent. By use of the lubricating agent, the developing agent carrier and the sliding contact surfaces can be kept highly lubricated. Accordingly, noise generated from the developing agent carrier and the sliding contact surfaces can be dramatically reduced. At the same time, toner leaks from the both ends of the developing agent carrier can be prevented to the extent there is no serious problem, i.e., there is minimal transfer of leaked toner onto the printed medium.
Further, a developing agent stopper may be provided at a lower-end front edge of a developing agent container to stop the developing agent on a bottom surface of the container. In case the developing agent leaks from any developing agent leak prevention member, the leaking developing agent can be stopped by the developing agent stopper, causing no contamination with the developing agent of an operator""s hands or the inside of the image forming apparatus.
The developing agent stopper is formed by a film member affixed to the lower-end front edge of the container or a resin member assembled to the container. Accordingly, the developing agent stopper is very easy to mount, yet can effectively stop the developing agent.
When the developing agent stopper is formed integrally with the container, it requires no assembling work and will improve assembling efficiency of the developing device.
A process cartridge provided with the above-described developing device tends to receive impacts when it is detached/attached. In such a case, no developing agent leaks from the periphery of the developing agent carrier, causing no contamination with the developing agent of the inside of the process cartridge, the inside of the image forming apparatus, or the surface where the image forming apparatus is installed.
Further, the developing device may be structured to be a detachable developing device cartridge and may be mounted in the process cartridge. In this case, similarly to the above case, no contamination with the developing agent is caused.
Recent-model image forming apparatuses often use polymerized toner as the developing agent. The polymerized toner has a very small particle size and is suitable for forming fine images. On the other hand, the polymerized toner has a high flowability and is likely to leak from the developing device. When the polymerized toner is used in the developing device in accordance with the invention, toner leaks from the ends of the developing agent carrier, which are the most leak-prone, are reliably prevented, causing no contamination of the surroundings with the toner.